Treating Fibrous Insulation To Reduce Thermal Conductivity

Monday, 27 July 2009

A chemical treatment reduces the
convective and radiative contributions
to the effective thermal conductivity of
porous fibrous thermal-insulation tile.
The net effect of the treatment is to
coat the surfaces of fibers with a mixture
of transition-metal oxides (TMOs)
without filling the pores. The TMO
coats reduce the cross-sectional areas
available for convection while absorbing
and scattering thermal radiation in
the pores, thereby rendering the tile
largely opaque to thermal radiation.

The treatment involves a sol-gel
process: A solution containing a mixture
of transition-metal-oxide-precursor salts
plus a gelling agent (e.g., tetraethy-lorthosilicate)
is partially cured, then,
before it visibly gels, is used to impregnate
the tile. The solution in the tile is
gelled, then dried, and then the tile is
fired to convert the precursor salts to the
desired mixed TMO phases. The
amounts of the various TMOs ultimately
incorporated into the tile can be tailored
via the concentrations of salts in
the solution, and the impregnation
depth can be tailored via the viscosity of
the solution and/or the volume of the
solution relative to that of the tile. The
amounts of the TMOs determine the
absorption and scattering spectra.

This work was done by Alfred Zinn and
Ryan Tarkanian of The Boeing Co. for
Johnson Space Center.

Title to this invention, covered by U.S.
Patent No. 7,198,839 B2, has been waived
under the provisions of the National
Aeronautics and Space Act {42 U.S.C. 2457
(f)}. Inquiries concerning licenses for its commercial
development should be addressed to:

The Boeing Company
5301 Bolsa Ave,
Huntington Beach, CA 92647-2099

Refer to MSC-23394-1, volume and number
of this NASA Tech Briefs issue, and the
page number.

This Brief includes a Technical Support Package (TSP).

Treating Fibrous Insulation To Reduce Thermal Conductivity (reference MSC-23394-1) is currently available for download from the TSP library.